Method of freezing with the aid of a cooling arrangement having a secondary refrigeration system and primary absorption refrigeration apparatus associated therewith

ABSTRACT

A freezer in which goods are frozen and already frozen goods are stored, such freezer embodying primary absorption refrigeration apparatus and a secondary refrigeration system associated therewith. The evaporator of the primary absorption refrigeration apparatus has a first part operable at a low temperature and a second part operable at a higher temperature. The second part of the primary evaporator operable at the higher temperature is employed to freeze goods. The secondary refrigeraton system contains a heat transfer fluid and has a condensation portion in heat exchange relation with the first part of the primary evaporator operable at the low temperature and an evaporation portion employed to maintain frozen already frozen goods.

United States Patent Blomberg 1 Feb; 18,1975

[ METHOD OF FREEZING WITH THE AID OF A COOLING ARRANGEMENT HAVING A SECONDARY REFRIGERATION SYSTEM AND PRIMARY ABSORPTION REFRIGERATION APPARATUS ASSOCIATED THEREWITH [75] Inventor: Peter Erik Blomberg, Stockholm,

Sweden [73] Assignee: Aktiebologet Electrolux, Stockholm,

Sweden [22] Filed: Apr. 17, 1974 21 App1.No.:461,784

Related US. Application Data [62] Division of Ser. No. 405,153. Oct. 10, 1973 [52] US. Cl. 62/65, 62/333 [51] Int. Cl F25b 15/10 [58] Field of Search 62/65, 333

[56] References Cited UNITED STATES PATENTS 2,261,681 11/1941 Ullstrand .v 62/333 Hedlund 62/333 Primary Examiner-William F. ODea Assistant Examiner-Peter D. Ferguson [57] ABSTRACT A freezer in which goods are frozen and already frozen goods are stored, such freezer embodying primary absorption refrigeration apparatus and a secondary refrigeration system associated therewith. The evaporator of the primary absorption refrigeration apparatus has a first part operable at a low temperature and a second part operable at a higher temperature. The second part of the primary evaporator operable at the higher temperature is employed to freeze goods. The secondary refrigeraton system contains a heat transfer fluid and has a condensation portion in heat exchange relation with the first part of the primary evaporator operable at the low temperature and an evaporation portion employed to maintain frozen already frozen goods.

3 Claims, 8 Drawing Figures PATENTED FEB l 8 I975 SHEET 1 OF 7 PATEHTED 1 81975 $866,429

' SHEET a [)F 7 PATENTEU FEB 1 5 866.42%

SHEET 5 BF 7 METHOD OF FREEZING WITH THE AID OF A COOLING ARRANGEMENT HAVING A SECONDARY REFRIGERATION SYSTEM AND PRIMARY ABSORPTION REFRIGERATION APPARATUS ASSOCIATED THEREWITH This application is a division of my application Ser. No. 405,153, filed Oct. 10,1973.

BACKGROUND OF THE INVENTION 1. Field of the Invention Freezers are available on the market in the form of chests which are operated by primary absorption refrigeration apparatus and secondary refrigerating systems associated therewith. Freezers of this type are particularly useful in areas where there is no source of electrical supply and the freezer of necessity must be operated by a fluid fuel burner, such as a gaseous fuel burner or a kerosene burner, for example.

2. Description of the Prior Art Freezers of the kind referred to above can be employed only for storing frozen goods and their freezing capacity has been comparatively small. Due to the specific properties of absorption refrigeration apparatus, it has not been considered possible heretofore to provide a freezer operated by absorption refrigeration apparatus having adequate refrigerating capacity at very low temperatures for storing already frozen goods and for freezing goods.

For this reason freezers of the type heretofore provided have only one space in which goods can be placed. This means that storing of already frozen goods and freezing of goods must be effected in the same space which adversely affects the temperature of frozen goods therein when fresh goods are placed in the space to be frozen.

Moreover, it has been brought out in the literature that the gas heat exchanger of absorption refrigeration apparatus is a primary obstacle in the development of such apparatus having optimum efficiency for storing already frozen goods and freezing goods. To overcome this problem it has been proposed to provide gas heat exchangers having several parallel paths of flow for the gas. Even if this form of gas heat exchanger possibly could solve the problem, it does not appear to be very attractive from a practical viewpoint. Moreover, a gas heat exchanger of this kind is prohibitive in cost.

SUMMARY OF THE INVENTION It is an object of my invention to provide a method of freezing with the aid of an improved cooling arrangement having a primary absorption refrigeration apparatus and a secondary refrigeration system associated therewith, whereby adequate refrigerating capacity at a very low temperature can be produced both for storing already frozen goods and freezing goods.

Another object is to provide such a method of freezing in which a second part of the primary evaporator, which is operable at a higher temperature than a first part thereof, is employed to freeze goods, and an evaporation portion of the secondary refrigeration system is employed to maintain already frozen goods in a freezing state, the condensation portion of which is in heat exchange relation with the first primary evaporator part at the low temperature.

I accomplish this by placing goods to be frozen in heat exchange relation with the second higher temperature part of the primary evaporator to abstract heat from such goods. Heat is transferred from the place of condensation of the secondary refrigeration system to the first low temperature part of the primary evaporator to condense heat transfer fluid in the condensation portion. Already frozen goods is placed in heat exchange relation with the evaporation portion of the secondary refrigeration system for evaporating heat transfer fluid therein by heat abstracted from such goods to maintain the latter frozen.

The temperature at which refrigerant evaporates in the second higher temperature part of the primary evaporator decreases as the goods to be frozen and in heat exchange relation with such higher temperature part approaches a freezing state, so that the refrigerating load on the primary evaporator is reduced.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a fragmentary side view, in section, of a freezer and a cooling arrangement therefor embodying the invention which is provided by a secondary refrigeration system and a primary absorption refrigeration apparatus of the inert gas type associated therewith;

FIG. 2 is a rear elevational view, partly broken away, of the freezer shown in FIG. 1, the parts of the secondary refrigeration system associated with the evapora' tor of the primary refrigeration apparatus being omitted;

FIG. 3 is a horizontal sectional view of the freezer taken at line 33 of FIG. 1, the secondary refrigeration system being omitted;

FIG. 4 is a front isometric view of the interior of the freezer shown in FIGS. I and 3 with the front closure member omitted;

FIGS. 5, 6 and 8 are fragmentary front views of the interiors of freezers like that shown in FIG. 4 illustrating modifications of the invention; and

FIG. 7 is a fragmentary vertical side view of parts of primary refrigeration apparatus, like those seen at the rear of the freezer shown in FIG. 1, illustrating another modification of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1, 2 and 3, l have shown my invention in connection with a freezer comprising a cabinet 10 having an inner liner 11 arranged to be supported within an outer shell 12 and insulated therefrom at 14 in any suitable manner. The inner liner ll defines a thermally insulated interior 15 to which access is afforded at a front opening adapted to be closed by an insulated door 16 hinged in any suitable manner (not shown) at the front of the freezer cabinet 10.

The freezer is provided with primary absorption refrigeration apparatus of the inert gas type. Refrigeration apparatus of this type comprises a generator 17 containing a refrigerant, such as ammonia, in solution in a body of absorption liquid, such as water. As shown in FIG. 2, heat can be supplied to the generator 17 from a heating tube 18 which may be heated by an electrical heating element 19, for example, which is disposed within the tube and connected by conductors 20 to a source of electrical supply at 21. The heat supplied to the generator 17 and absorption solution expels refrigerant vapor out of solution, and, in a manner to be described hereinafter, refrigerant vapor passes upward from the generator through a vapor supply line or conduit 22 into an air-cooled condenser 23 in which vapor is liquefied by surrounding cool air which flows in physical contact therewith and heat dissipating members 24 fixed thereto. The liquefied refrigerant flows from the condenser 23 through conduits 25 and 26 into one end 27a of an evaporator 27 disposed in the upper part of the cabinet interior 15.

The evaporator 27, which comprises a looped coil having straight sections and connecting bends, is horizontally disposed and extends between the opposing vertical sides of the cabinet 10, as best shown in FIGS. 3 and 4. The liquefied refrigerant evaporates and diffuses into an inert pressure equalizing gas, such as hydrogen, which flows upward through a first looped coil 28 of a gas heat exchanger 29 and passes from the upper end thereof into the end 27a of the evaporator 27 into the presence of the refrigerant. Due to evaporation of refrigerant into inert gas in the evaporator 27, a refrigerating effect is produced with consequent absorption of heat from the surroundings.

The rich gas mixture of refrigerant and inert gas formed in the evaporator 27 flows downward from the other end 27b thereof through a second looped coil 30 of the gas heat exchanger 29 and a vertical conduit 31 into an absorber comprising a vessel 32 and a looped coil 33. In the absorber vessel 32 and looped coil 33 refrigerant vapor is absorbed into liquid absorbent, such as water, which enters through a conduit 34 in heat exchange relation with the conduit 31. The hydrogen or inert gas, which is practically insoluble and weak in refrigerant, is returned to the end 27a of evaporator 27 from the upper end of the absorber coil 33 through the upper part of conduit 34 and first looped coil 28 of the gas heat exchanger 29.

The first and second looped coils 28 and 30 of the gas heat exchanger 29, in a lengthwise direction, are in heat exchange relation, as best seen in FIG. 2. Further, the conduit 26 through which liquid refrigerant flows to the evaporator 27, is disposed about the second looped coil 30 and in heat exchange relation therewith. In this way heat exchange is effected between liquid refrigerant in its path of flow and cool rich gas mixture flowing downward in the second looped coil 30, so that liquid refrigerant will be pre-cooled before it flows into the presence of inert gas at the inlet end 27a of the evaporator 27.

The extreme upper end of the first looped coil 28 comprises a bent pipe section 28a which is of inverted V-shape with its apex at 35. It will be seen that the conduit 26 at its upper end is connected to the bent pipe section 28a at 36 below its apex 35. In this way liquid refrigerant and weak inert gas are both introduced into the evaporator 27 at the same end 27a for parallel flow therethrough.

Absorption liquid enriched in refrigerant in the absorber flows from the vessel 32 through an outer passageway 37 of an elongated liquid heat exchanger 38 which, within the generator 17, includes an outer vertical pipe 39 and an inner vertical pipe 40. Rich absorption liquid flows from the passageway 37 through a horizontal conduit 41 into a vertical standpipe 42. The conduit 41 is connected to standpipe 42 at a point 43 which is at a level below the liquid surface level 44 of the liquid held in the pipe 42. As seen in FIG. 2, the liquid surface level 44 is at approximately the same level as the liquid surface level in the absorber vessel 32.

The extreme lower end of the pipe 42 is connected to the lower end of the pump pipe or vapor-liquid lift tube 45 heat conductively connected to heating tube 18 at 46', as by welding, for example. Liquid is raised by vapor-liquid lift action through the tube or pump pipe 45 into the upper part of the pipe 40. Alternatively, a gaseous fuel burner 19a, which is connected by a conduit 20a to a source of supply of gaseous fuel, may be employed to heat a heating flue 18a heat conductively connected to the pump pipe 45. As seen in FIG. 2, the heating flue 18a extends vertically through the generator 17. Suitable controls (not shown), similar to the controls provided for the heating element 19 and described hereinafter, may be employed to control the flow of gaseous fuel to the burner 19a.

The absorption liquid from which refrigerant vapor has been expelled flows downward by gravity through the liquid heat exchanger 38 and forming an inner passageway thereof. The pipe 40 is connected to the conduit 34 from which absorption liquid overflows into the upper end of the absorber coil 33 at a point 33a which is below the liquid surface level 40a in the pipe 40.

The generator 17, together with a part of the liquid heat exchanger 38, are embedded in a body of insulation 46 retained in a metal shell or casing 47 having an opening 48a in the bottom 48 thereof. The electrical heating element 19, with the conductors 20 connected thereto, is arranged to be positioned within the heating tube 18 through the opening 48a in any suitable manner (not shown).

In the operation of the refrigeration apparatus, vapor generated in the vapor-liquid lift pump 45 flows from the upper end thereof to a gas separation chamber 40b at the extreme upper end of the standpipe 40 and passes through openings 40c in the side wall thereof in the outer passage 49 formed between the inner and outer pipes 40 and 39, respectively. The vapor in the passage 49 depresses the liquid level therein to a point 50 and flows through enriched liquid in conduit 41 and pipe 42 by bubble action. After the generated vapor is analyzed in this manner in the conduit 41 and pipe 42, the refrigerant vapor passes from the upper part of the pipe 42 and vapor supply line 22 to the condenser 23, as previously explained.

The condenser 23 is connected by a conduit 51 to a part of the gas circuit, as to the conduit 31, for example, so that any inert gas which may pass through the condenser 23 can flow to the gas circuit.

With the evaporator 27 positioned in the compartment 15 of the cabinet 10, the other components of the refrigeration apparatus are located in a vertically extending apparatus space 52 at the rear of the cabinet. Natural draft is produced in the space 52 and causes upward circulation of ambient air due to heat radiated by absorber vessel 32 and coil 33 and by the condenser 23, so that surrounding cool air can flow directly over their surfaces and assure adequate cooling of these parts or components. The top and bottom of the space 52 are open to enable air to flow freely upward therein.

As best shown in FIGS. 1, 2 and 3, the gas heat exchanger 29, which extends across the cabinet 10 between the lateral sides thereof, is disposed within a body of insulation 14a retained in a removable wall section 53 of the rear insulated wall 54 to facilitate the insertion of the evaporator 27 within the cabinet. The lower part of the gas heat exchanger 29, which is transverse thereto and formed by the lower ends 28b and 30b of the looped coils 28 and 30, respectively, projects rearwardly from the body of insulation into the apparatus space 52, as shown in FIG. 1. The removable wall section 53 closes an opening in the rear insulated wall 54 and is removably secured thereto in any suitable manner (not shown).

A control device 55 is operatively associated with a switch 56 connected in one of the conductors for supplying electrical energy to heating element 19. The control device 55 is thermostatically controlled and is provided with a capillary tube 57 and thermal sensitive bulb 58 adapted to contain a suitable volatile fluid, the bulb 58 being arranged to be influenced by the temperature of air in the cabinet interior 15 which is cooled by the evaporator 27. The control device 55 functions to control switch 56 responsive to a temperature condition affected by the evaporator 27 and may be provided with a control knob 55a to adjust the temperature at which it is desired to maintain the evaporator 27.

As pointed out above, the evaporator 27 comprises a looped coil extending horizontally across the cabinet interior 15 between the lateral side walls of the cabinet 10 and divides the interior into top and bottom spaces 62 and 63, respectively. As seen in FIGS. 3 and 4, the evaporator 27 has one part 60 near the end 270 thereof at which liquid refrigerant and inert gas weak in refrigerant are introduced into the evaporator; and another wide part 61 from which inert gas passes from the evaporator 27 at the opposite end 27b.

The evaporator 27 provides an elongated path of flow for the inert gas and has a temperature gradient in which the temperature progressively increases from a first temperature at its one end at 270 to a second higher temperature at its other end at 27b. This is so because, since the inert gas flows horizontally in the evaporator 27 from its one end at 27a to its other end at 27b, the gas in the part 60 contains a lesser amount of refrigerant vapor than the gas in the wider part 61. The partial vapor pressure of the refrigerant is a gradient, so that the temperature of liquid refrigerant in the evaporator 27 also is a gradient, the evaporating tem perature being lower in the part 60 of the evaporator and higher at the part 61 thereof.

ln accordance with my invention the higher temperature part 61 of the evaporator 27, which will be referred to as the primary evaporator, is employed to abstract heat from goods in the top space 62 to freeze such goods; and the low temperature part 60 of the primary evaporator, with the aid of a secondary refrigeration system 64, is employed to abstract heat from already frozen goods in the bottom space 63 in which such goods are stored.

The secondary heat transfer system 64 includes a condensation portion 65, evaporation portions 66 and connecting conduits 67,68,69 and 70. The condensation portion 65 is in the form of a looped coil arranged in thermal exchange or heat conductive relation with the low temperature part 60 of the primary evaporator 27.

The secondary evaporation or heat abstracting portions 66 of the heat transfer path each comprises a shelf in the form ofa looped coil which are in spaced relation in the bottom space 63.

The condensation portion 65, evaporation portions or coils 66 and connecting conduits 67,68,69 and 70 form a closed fluid circuit which contains a suitable volatile fluid, such as dichlorodifluoromethane, at an appropriate pressure. The volatile fluid evaporates within the shelf coils 66 and takes up heat thereby transmitting cooling effect and cooling the bottom space 63.

The system may be filled with liquid to a point above the top shelf coil 63, whereby the shelf coils constitute evaporation members of the flooded type for holding the volatile fluid in heat transfer relation to the shelves. The vapor flows upward through liquid in the shelfcoils and the connecting conduits 67, 68 and 69 into the condensation portion 65. The vapor is cooled and condensed in the condensation portion 65 by the low temperature part of the primary evaporator 27. The condensate flows downward through conduit 70 and back into the shelf coils 66 where it is again evaporated. Hence, cooling effect is transmitted by the low temperature part 60 of the primary evaporator to the secondary refrigeration or heat transfer system 64 with such system conducting heat therethrough to transmit cooling effect to the coil shelves 66.

A metal plate 71 having good thermal conducting properties is fixed in any suitable manner (not shown) to the top of the higher temperature part 61 of the primary evaporator 27 to increase the heat transfer sur' face to freeze goods in heat exchange relation therewith. The low temperature part 60 of the primary evaporator 27 and condensation portion of the secondary refrigeration system 64 are retained in heat exchange relation with one another within a housing 72.

The primary evaporator 27 of the absorption refrigeration apparatus desirably operates at very low temperatures with the low temperature part 60 thereof operating in a temperature range of 30C. and 22C. While the remaining part 61 of the primary evaporator 27 operates at a somewhat higher temperature it is nevertheless below the temperature required for storing frozen goods and in a range of -22C. and -19C., for example.

When frozen goods are held in both the top and bottom spaces 62 and 63, the primary evaporator 27 in its entirety operates in a temperature range below the temperature required for storing of such goods, such as 30C. and 19C., for example. This operating condition is maintained by the thermostatic control 55 described above and shown in FIG. 4 when the absorption refrigeration apparatus is operated by the electrical heating element 19 and by a similar thermostatic control (not shown) when the apparatus is operated by the gas burner 19a.

Goods to be frozen are held in the top space 62 in thermal exchange relation with the plate 71. Such goods desirably should be pre-cooled in a refrigerator to a temperature of about +5C. and then transferred to the top space 62 in the freezer cabinet 10. When this occurs the temperature of the higher temperature part 61 of the primary evaporator 27 changes considerably. To start with, the higher temperature part 61 of the evaporator 27 will operate in a temperature range of about 22C. and 5C. Due to the manner in which evaporation of refrigerant into inert gas takes place in the primary evaporator 27, as explained above, heat will be abstracted from the top space 62 and goods therein to the higher temperature evaporator part 61 at a rate several times greater than before. The absorption refrigeration apparatus under these conditions will operate continuously without interruption and the temperature of the high temperature evaporator part 61 will not fall to a sufficiently low temperature for the thermostatic control 55 to become operable to open the switch 56 and disconnect the electrical heating element 19 from the source of electrical supply at 21. Therefore, the goods in the top space 62 will be frozen relatively fast although the efficiency of the primary absorption refrigeration apparatus, when the evaporator thereof is operating at a freezing temperature for storing goods in its freezer, must be considered to be limited compared with other types of refrigeration appara- 1.15.

As freezing of the goods in the top space 62 continues, the temperature at which the higher temperature evaporator part 61 operates will fall and become less and less and heat will be abstracted from the top space 62 and goods therein to the evaporator part 61 at a reduced rate. Hence, the temperature at which refrigerant evaporates into inert gas in the higher temperature evaporator part 61 of the primary evaporator 27 decreases as the goods to be frozen and in heat exchange relation with such higher temperature evaporator part 61 approaches a freezing state and reduces the refrigerating load on the primary evaporator 27.

When freezing of the goods in the top space 62 is completed the refrigerating capacity of the primary absorption refrigeration apparatus will be greater than actually needed. When this occurs the thermostatic control 55 will commence to function in a normal manner and control the operation of the refrigeration apparatus to hold the temperature of the primary evaporator 27 substantially at a predetermined temperature.

When the absorption refrigeration apparatus is operated electrically, as shown in FIG. 2, suitable means like a glow lamp (not shown), for example, may be connected in the electric circuit in which the thermostat control is connected to indicate when freezing of goods in the space 62 is completed.

FIG. illustrates a modification of the invention shown in FIG. 4 in which parts similar to those in the first described embodiment are referred to by the same reference numerals to which 100 has been added. In FIG. 5 the primary evaporator 127 divides the interior 115 of the cabinet 110 into top and bottom spaces 162 and 163, respectively.

The condensation portion 165 of the secondary refrigeration system 164 is in thermal exchange relation with the low temperature part 160 of the primary evaporator 127. The condensation portion 165 is connected by conduits 169 and 170 to shelf coils (not shown) like the shelf coils 66 shown in FIG. 4.

In FIG. 5 the plate 171 fixed to the top of the higher temperature part 161 of the primary evaporator 127 includes a portion 171a which projects beyond the higher temperature part 161 and overlies the low temperature part 160. In order to thermally shield the low temperature evaporator part 160 from the top space 162 and goods therein, a member 73 formed of heat insulating material is interposed between the portion 171a of the plate 171 and the low temperature evaporator part 160.

FIG. 6 illustrates another modification of the invention shown in FIG. 4 in which parts similar to those in the first described embodiment are referred to by the same reference numerals to which 200 has been added. In FIG. 6 the primary evaporator 2'27 divides the interior 215 of the cabinet 210 into top and bottom spaces 262 and 263, respectively.

The condensation portion 265 of the secondary refrigeration system 264 is in thermal exchange relation with the low temperature part 260 of the primary evaporator 227. The condensation portion 265 is connected by conduits 269 and 270 to shelfcoils (not shown) like the shelf coils 66 shown in FIG. 4.

In order to thermally shield the higher temperature evaporator part 261 from the bottom space 263 and goods therein, a member 74 formed of heat insulating material is positioned at the underside of the higher temperature evaporator part 261. The heat insulating member 74 is removable held on hooks 75' depending downward from the higher temperature evaporator part 261. The plate 271 fixed to the top ofthe higher temperature evaporator part 261 is provided with side walls 271a extending. upward to the ceiling of the top space 262.

It will be understood that in FIG. 4 the bottom of the higher temperature part 61 of the primary evaporator 27 can be thermally shielded from the bottom space 63 by a heat insulating member like the member 74 in FIG. 6. Also, it will be understood that in FIG. 4 the top of the low temperature part 60 of the primary evaporator 27 can be thermally shielded from the top space 62 by a heat insulating member like the member 73 in FIG. 5.

A modification like that just described which includes both heat insulating members like the members 73 and 74 in FIGS. 5 and 6, respectively, is illustrated in FIG. 8. In FIG. 8 parts similar to those in the first described embodiment of FIGS. 1 to 4 and modifications of FIGS. 5 and 6 are referred to by the same reference numerals to which 400 has been added.

In FIG. 8 the primary evaporator 427 divides the interior of the cabinet 410 into top and bottom spaces 462 and 463, respectively.

The condensation portion 465 of the secondary refrigeration system 464 is in thermal exchange relation with the low temperature part 460 of the primary evaporator 427. The condensation portion 465 is connected by conduits 469 and 470 to shelf coils (not shown) like the shelf coils 66 shown in FIG. 4.

In FIG. 8 the plate 471 is fixed to the top of the higher temperature part 461 of the primary evaporator 427. In order to thermally shield the low temperature part 460 from the top space 462 and goods therein, a member 473 formed of heat insulating material is interposed between an extension 471a of the plate 471 and the low temperature evaporator part 460 in the manner shown in FIG. 5.

In order to thermally shield the higher temperature evaporator part 461 from the bottom space 463 and goods therein, a member 474 formed of heat insulating material is positioned at the underside of the higher temperature evaporator part 461. The heat insulating member 474 is removably held on hooks 475' depending downward from the higher temperature evaporator part 461 in the manner shown in FIG. 6.

Although the low and higher temperature evaporator parts 60 and 61 in FIG. 4 are not thermally shielded from the top and bottom spaces 62 and 63, respectively, of the cabinet interior 15 in the manner illustrated in FIG. 8 and just described. it should be understood that the higher temperature evaporator part 61 in FIG. 4 will primarily be effective to abstract heat from the top space 62 and goods therein and the low temperature evaporator part 60 in FIG. 4 will primarily be effective to abstract heat from the bottom space 63 and goods therein. In FIG. 4 this is accomplished by arranging the higher temperature evaporator part 61 in thermal exchange relation with the underside of the horizontal plate 71. The plate 71, together with the housing 72, separates the top and bottom spaces 62 and 63 to prevent circulation of air therebetween. Further, the condensation portion 65 of the secondary heat transfer system is in thermal exchange relation with the low temperature evaporator part 60. Also, the housing 72 separates the top and bottom spaces 62 and 63, and, together with the plate 71, segregates these spaces to prevent circulation of air therebetween. Hence, even though the first described embodiment of FIG. 4 does not provide thermal shielding of the low and higher temperature parts in the manner illustrated in FIG. 8, these evaporator parts and the horizontal plate 71 and condenser 65 of the secondary heat transfer system 64 and housing 72 are associated with one another in such manner that the evaporator parts 61 and 60 will be primarily effective to abstract heat from the top and bottom spaces 62 and 63, respectively, of the cabinet interior 15.

In the embodiment of FIGS. 1 to 4 the condenser 23 is cooled by natural draft in the space 52 at the rear of the cabinet 10, as pointed out above. When the ambient temperature is relatively high it is desirable to sup plement such natural draft cooling of the condenser by forced draft cooling to insure that condensed refrigerant will be supplied at an adequate rate to the evaporator 27 from the condenser.

Such a modification is shown in FIG. 7 in which parts similar to those shown in FIG. 1 are referred to by the same reference numerals to which 300 has been added. In FIG. 7 a fan 75 is disposed in the rear apparatus space 352 which supplements natural draft circulation of air and forces cooling air upward over the surfaces of the condenser 323 and cooling fins 324 fixed thereto. The fan 75 is driven by an electric motor 76 mounted on a bracket 77 fixed to the rear wall 354 of the cabinet 310.

The motor 76 is connected in a circuit having conductors 78 and 79 which are connected by conductors 80 and 81 to a source of electric supply. Thermoelements 82 and a bi-metallic switch 83 are connected in the fan motor circuit. The thermoelements 82 are mounted on the flue 318a in good heat conductive contact therewith by a bracket 84. Hence, the thermoelements 82 of the fan motor circuit will be closed only when the absorption refrigeration apparatus is operating and the gas burner 319a is supplying heat to the generator 317.

Further, the fan motor circuit will be completed and energize the motor 76 only when the ambient air is at a predetermined temperature, such as 35C., for example, at which temperature the bi-metallic switch 83 will be closed.

It will be understood that the freezer embodying the invention, which has been described above and shown in the drawing, is provided with comparatively thick insulation, such as polyurethane foam containing a heavy gas like trichloromonofluormethane, for example. Further, the capacity of the gas heat exchanger 29 relative to other components of the absorption refrigeration apparatus is greater than that of gas heat exchangers of conventional absorption refrigeration apparatus. Any unevaporated refrigerant passing from the end 271) of the evaporator 27 will evaporate into inert gas flowing downward in the looped coil 30 of the gas heat exchanger.

I claim:

1. In the art of freezing goods to be frozen and maintaining already frozen goods frozen with a primary refrigeration system employing an inert gas into which liquid refrigerant evaporates in a primary place of evaporation and a secondary refrigeration system having a heat transfer fluid which condenses in a place of condensation and evaporates in a place of evaporation, the liquid refrigerant evaporating into inert gas at a low temperature in a first part of said primary place of evaporation and at a higher temperature in a second part of said primary place of evaporation, the improvement which comprises a. placing goods to be frozen in heat exchange relation with the second higher temperature part of said primary place of evaporation for the latter to abstract heat from such goods,

b. transferring heat to the first low temperature part of said primary place of evaporation from the place of condensation ofsaid secondary refrigeration system to condense heat transfer fluid therein, and

c. placing already frozen goods in heat exchange rela tion with the place of evaporation of said secondary refrigeration system for evaporating heat transfer fluid therein by heat abstracted from such goods to maintain the latter frozen,

(1. the temperature at which refrigerant evaporates into inert gas in the second higher temperature part of said primary place of evaporation decreasing as the goods to be frozen and in heat exchange relation with such higher temperature part approaches a freezing state and reduces the refrigerating load on the primary place of evaporation.

2. The improvement set forth in claim 1 in which the goods to be frozen, before being placed in heat exchange relation with the second higher temperature part of said primary place of evaporation, is pre-cooled.

3. The improvement set forth in claim 1 in which the goods to be frozen, before being placed in heat exchange relation with the second higher temperature part of said primary place of evaporation, is pre-cooled to a temperature of about +5C. 

1. In the art of freezing goods to be frozen and maintaining already frozen goods frozen with a primary refrigeration system employing an inert gas into which liquid refrigerant evaporates in a primary place of evaporation and a secondary refrigeration system having a heat transfer fluid which condenses in a place of condensation and evaporates in a place of evaporation, the liquid refrigerant evaporating into inert gas at a low temperature in a first part of said primary place of evaporation and at a higher temperature in a second part of said primary place of evaporation, the improvement which comprises a. placing goods to be frozen in heat exchange relation with the second higher temperature part of said primary place of evaporation for the latter to abstract heat from such goods, b. transferring heat to the first low temperature part of said primary place of evaporation from the place of condensation of said secondary refrigeration system to condense heat transfer fluid therein, and c. placing already frozen goods in heat exchange relation with the place of evaporation of said secondary refrigeration system for evaporating heat transfer fluid therein by heat abstracted from such goods to maintain the latter frozen, d. the temperature at which refrigerant evaporates into inert gas in the second higher temperature part of said primary place of evaporation decreasing as the goods to be frozen and in heat exchange relation with such higher temperature part approaches a freezing state and reduces the refrigerating load on the primary place of evaporation.
 2. The improvement set forth in claim 1 in which the goods to be frozen, before being placed in heat exchange relation with the second higher temperature part of said primary place of evaporation, is pre-cooled.
 3. The improvement set forth in claim 1 in which the goods to be frozen, before being placed in heat exchange relation with the second higher temperature part of said primary place of evaporation, is pre-cooled to a temperature of about +5*C. 